Elevated tumour marker CA19-9: clinical interpretation and influence of obstructive jaundice

Aims: The tumour marker CA19-9 hat; been promoted as a reliable test for th e detection of pancreatobiliary malignancy, yet its diagnostic role remains poorly defined. In this study the clinical interpretation of a raised seru m CA19-9 level has been evaluated, with particular reference to obstructive jaundice. Methods: One hundred and sixty-four patients with a CA19-9 level above 33 U /ml were studied. Serum CA19-9 was compared with clinical diagnosis and cor related with serum bilirubin level. In a subgroup of jaundiced patients (16 benign and 15 malignant cases): follow-up CA19-9 levels were determined 2 weeks after biliary drainage. Results: The median CA19-9 level was lower in benign cases (102 (IQR 50-264 ) U/ml) than those with pancreatobiliary tumours (910 (IQR 263-6170) U/ml; P<0.01), although the overlap was substantial. In benign jaundiced cases, a positive correlation was observed between bilirubin and CA19-9 elevation ( R = 0.41, P<0.01). Relief of jaundice was associated with a fall in CA19-9 level in all benign cases and in nine of the 15 with malignancy. Conclusion: Confident discrimination between benign and malignant disease c ould not be made on the basis of a solitary elevated CA19-9 measurement. Hy perbilirubinaemia was associated with a further deterioration in specificit y and caution is warranted when interpreting the results in jaundiced patie nts. Overall, only one half of patients with an elevated CA19-9 level ultim ately proved to harbour a malignancy. (C) 2000 Harcourt Publishers Ltd.